Effects of Al₂O₃ and MgO on Softening, Melting, and Permeation Properties of CaO-FeO-SiO₂ on a Coke Bed

In ironmaking, maintaining gas permeability in blast furnace with low coke rate operation is essential to reduce carbon emissions. The high pressure loss in the cohesive zone decreases the gas permeability and affects the productivity of blast furnace. In order to increase the gas permeability in the cohesive zone, the thickness of the cohesive layer should be decreased. For this purpose, increasing softening temperature and decreasing dripping temperature of the iron ore are desired. In this study, softening, melting, and permeation of SiO₂-FeO-CaO-Al₂O₃-MgO on a coke bed were investigated. The oxide sample in a tablet form was heated under CO/CO₂ atmosphere, and the shape of the tablet was observed. The softening and melting temperatures of the SiO₂-FeO-CaO system changed with the addition of Al₂O₃ and MgO. Oxide tablets with and without Al₂O₃ softened below and above the solidus temperature, respectively. The melting temperatures varied with the ratio of CO/CO₂ in the gas. The permeation temperature was independent of the melting temperature, but dependent on the wettability.